Take a good strong flashlight. Look in the rear under the storage hatch (covers ... lids .. whatever ya' call em'), for a small indentation and the key ... which is also a dark color ... should be in there.
Black carpets, dark hatch and a dark key ... it was a bit tough to spot.
My former mechanic charged me something like $170 to "break" the lugs off when he was doing the tires because he couldn't find it.
I missed it too when I got the car home but after someone on this forum told me where to look ... once I did a second search ... with a small flashlight, I found it right off.